Diazo film developer

ABSTRACT

A diazo film developer and method of developing roll-type diazo film, continuously fed into the developer through a seal, wherein the film is (1) subjected to a cycled air mixture containing water vapor cooled to the dew point whereby a water condensate is deposited on the surface of the film, (2) simultaneously subjected to an ammonia vapor which is absorbed by the water condensate to develop the film, (3) subsequently subjected to the cycled air mixture preheated to dry the film and scavenge excess ammonia gas.

nited States Patent 1191 Hurtig et al.

[ 51March 13, 1973 DIAZO FILM DEVELOPER [75] Inventors: Roy EugeneHurtig, Montesereno; Don Winston Geri, Sunnyvale; Paul Horst Becker, SanJose, all of Calif.

[73] Assignee: Memorex Corporation, Santa Clara,

Calif.

22 Filed: ,Feb. 16,1971

21 Appl.No.: 115,588

[52] U.S. Cl. ..95/94 G, 95/89 G [51] Int. Cl. ..G03d 7/00 [58] Field ofSearch ...95/89 R, 89 G, 94 R, 94 G [56] References Cited UNITED STATESPATENTS 10/1970 Muller l/l932 Langsner ..95/94G 4/1969 Goodman et al...95/94 R 2,630,744 3/1953 Wilde ..95/89 G 3,147,687 9/l964 3,323,4366/1967 Hafer et al ..95/89 G Primary ExaminerSamuel S. MatthewsAssistant Examiner-Fred L. Braun Attorney-Limbach, Limbach & Sutton 57ABSTRACT A diazo film developer and method of developing rolltype diazofilm, continuously fed into the developer through a seal, wherein thefilm is (1) subjected to a cycled air mixture containing water vaporcooled to the dew point whereby a water condensate is deposited on thesurface of the film, (2) simultaneously subjected to an ammonia vaporwhich is absorbed by the water condensate to develop the film,

,(3) subsequently subjected to the cycled air mixture preheated to drythe film and scavenge excess ammonia gas.

12 Claims, 7 Drawing Figures PATENTEDHAR 1 (H975 SHEET 1 0F 3 IN ENTORSROY EUGENE HURT/6 BY DON Wl/V5TON GEK/ PAUL HORST BECKER iflfi ATTORNEYSPIE .2.

DIAZO FILM DEVELOPER SUMMARY OF THE INVENTION Development of filmscontaining light sensitive diazo compounds is most commonly accomplishedwith ammonia solution or gas mixtures. After exposure to light,particularly ultraviolet light, the diazo compound decomposes. Theundecomposed diazo compound is prevented from reacting with a couplingcompound for developing contrast while in an acid medium. To inhibituncontrolled film development all film coatings are acidic. Ammonia isused in development to neutralize acid present in the film coating andto provide an alkaline medium in which the diazo coupling reaction canrapidly proceed.

It has been observed that operation with water is necessary in anammonia film processor to achieve any development. This is presumablydue to the fact that a liquid medium is needed in the film for thecoupling reaction to proceed rapidly. Further evidence for thisobservation is the fact that anhydrous ammonia systems only work atpressures that provide condensation of liquid ammonia at the operatingtemperature.

The principal problems in construction of a diazo film developer concernthe application of ammonia and the water carrier to the film in amountsproper for rapid development without wasteful excess.

Most of the prior art involves development of prints and copy paper. Theinstant invention provides a method and the apparatus for developing adiazo film strip which is continuously fed through the developer. Waterand ammonia requirements. must therefore be dept at a minimum if largequantities of film are to be rapidly developed in an apparatus ofacceptable size. Additionally, because of the caustic nature of ammoniahydroxide and unpleasant odor of ammonia gas, am-- BRIEF DESCRIPTION OFTHE DRAWINGS FIG. 1 is a perspective view of the diazo developer.

FIG. 2 is a plan view of the developer of FIG. 1.

FIG. 3 is an enlarged and. exploded view of a film seal on the developershown in FIG. 1.

FIG. 4 is a sectional view of the film seal.

FIG. 5 is a sectional view of the developer of FIG. 1.

FIG. 6 is a schematic of the film seal operation.

FIG. 7 is a schematic of an alternate film seal operation.

DETAILED DESCRIPTION OF THE INVENTION.

The diazo developer shown in FIG. 1 accepts film 10 to be developedthrough an entrance slot 12 in. a film seal 14 mounted to the upperportion 16 of the developer. As illustrated in both FIGS. 1 and 2', thefilm 10 is threaded around adjustable spools 18 and spools 20 usingexternal film drive means, and returned throughv an exit slot 22 in thefilm seal fully developed. A removable glass cover 24 provides easyaccess to the upper portion l6 of the developer for initial threading ofa film leader around the spools. Four clamps 26 fasten the glass coveragainst a rubber seal 28 on the rim of the upper portion of thedeveloper. The glass cover allows visual inspection of the filmdeveloping process as it occurs enabling an operator to make thoseadjustments necessary for the most efficient operation of the system andprovides for thermodynamic properties required by the basic cycle.

The upper portion 16 of the developer is divided by a vertical dam 30into a first chamber 32 and a second chamber 34. In the first chamber 32the film is subject to a cycled air mixture containing water vaporcooled to the dew point and an ammonia vapor which act to develop thefilm. In the second chamber 34 the film is subjected to the preheatedair mixture which dries the 'film and scavenges any excess ammonia fromthe previous developing process. The dam 30 forms a partial barrier tothe flow of the mixture of air and water vapor from the second chamber34 to the first chamber 32 forcing the flow upward and between the topof the dam 30 and the surface of the glass cover as indicated by theflow arrows shown in FIGS. 1 and 2, and in particular, FIG. 5.

When the air mixture flows through the narrow passage between the damand glass cover it is cooled to approximately its dew point as it entersthe first chamber 32.

The upper portion of the developer is separated from the lower portion36 by a floor plate 34 which supports the adjustable spools, spools anddam.

Located in a row on the floor plate in the second chamber arecirculation holes 42 which allow the air mixture to be cycled from thelower portion to the upper portion of the developer. Similarly,circulation holes 44 in the first chamber allow the air mixture to becycled from the upper portion to the lower portion. These circulationholes permit the cycled air mixture to continuously flow from the secondchamber to the first chamber.

' Ammonia vapor is introduced to the first chamber from an anhydrousammonia reservoir 46 contained in a remote container and enters throughan ammonia vent 48 in the floor plate. The venting is regulated by acontrol valve 50 as illustrated in FIG. 5. The ammonia vent 48 releasesammonia vapor initially into an ammonia tunnel 52 through which the filmpasses to insure that the film is subjected to an adequate ammoniasupply. From the ammonia tunnel 52 the majority of the ammonia isemitted to the first chamber where it is continually absorbed by thewater condensate that has been deposited on the film by the cooled airmixture until an equilibrium state is reached. As water and ammoniamixture is absorbed into the film surface the film is, developed.

The cyclical flow of the air mixture is most clearly shown in FIG. 5. Apump or blower S4 draws the air mixture from the first chamber 32through the circulation holes 44 in the floor plate 38 across atemperature sensor 60 to a third chamber 56 containing a water reservoir58. Here the air mixture picks up additional water vapor to approachsaturation before it is forced by the pressure from the blower 54through a heater 62. The heater 62 is regulated by the temperaturesensor 60 to control the degree to which the air mixture is raised abovethe dew point. Knowing the degree to which the air mixture is cooledwhen passing from the second chamber to the first, the temperaturesensor 60 ultimately controls the temperature of the air mixture in thefirst chamber. After the air mixture is passed through the heater itflows up an air passage 64 and through the circulation holes 42 in thefloor plate 38 to the second chamber 34 to scavenge any ammonia andwater from the film.

It can be readily perceived that the film developing process is closedto the outside atmosphere except at the point the film enters and exitsthe developer. To inhibit escape of noxious ammonia vapors from thedeveloper, a special film seal 14 has been constructed.

As noted hereinbefore the film as shown in FIG. 1 enters a slot 12 inthe film seal 14 and exits an identical slot 22 parallel to the entranceslot. The internal construction of the film seal 14 is most clearlyillustrated in the exploded view of FIG. 3 and the section view of FIG.4.

A pair of contoured side pieces 66 are fixed to opposite sides of acontoured center piece 68 that is mounted against the upper portion 16of the film developer.

The side pieces are cut with a wide groove on their contoured face 70 toform the entrance and exit slots, 12 and 22, when the side pieces areclamped to the center piece 68 by a spring clamp 72 as shown in FIGS. 1and 2. Scratching of the film is prevented by the adjustable spools 18which transport the film through the slot without the film coming incontact with the walls of the slot.

Also cut into the face 70 of the contoured side pieces, 66, are twointerlocking, U-shaped channels, 74a and 76a, respectively. The channelsmatch oppositely disposed U-shaped channels, 74b and 76b on eachcontoured face 78 of the center piece 68. The matching sets of channelsare interconnected by separate internal conduits, 74c and 76c, in thecenter piece and are respectively joined to a pressure supply line 74dand a vacuum supply line 76d as shown in FIG. 3.

As the film enters and exits the developer, it encounters two sets ofalternating pressure vacuum channels transversely disposed in theentrance and exit slots of the developer. As apparent from FIGS. 3 and4, the channel most internally disposed in each slot is a pressurechannel. Air is forced through the pressure line 74d to the pressurechannel to create a back pressure in the entrance and exit slots formingan air cushion to counteract the moderate pressures that build up in thedeveloper during operation. Adjacent to the pressure channel is thevacuum channel 76a and 76b wherein air circulation scrubs the film anddraws off excess air from the pressure channel 74a and 74b. The vacuumchannel also removes any of the internal atmosphere of the developerwhich permeates the air cushion. The second pressure channel is a backup which in combination with the final vacuum channel disposed adjacentto the slot entrance insures that escape of any of the ammonia ladenatmosphere in the developer is kept at an absolute minimum.Additionally, the film seal provides a final air scrubbing for theammonia developed film as it leaves the developer through the exit slot.

FIG. 6 and FIG. 7 schematically illustrate two alternate methods ofoperating the film seal 14. In FIG. 6 the film seal is operatedessentially as a closed loop. The vacuum line 76d draws air and anyescaping ammonia from the vacuum channels to an ammonia absorber 80which removes all of the air-mixed ammonia. An air pump 82, which drawsthe air from the seal returns the scrubbed air through flow controlvalve 84, and pressure line 74d to the film seal 14. Since air from theexternal atmosphere and excess ammonia are entrained in small quantitiesby the vacuum channels, 76a and 76b, a bleeder line with a bleeder valve88 is included to vent this excess air to the atmosphere.

In FIG. 7 an open system is provided for the seal 14. An air pump 90draws air and any contained ammonia from the vacuum channels throughvacuum line 76d and forces the air-ammonia mixture through flow controlvalve 84, thence through the ammonia absorber 80 which removes theammonia before the air is vented to the atmosphere. The separatelyoperated pressure line 74d'draws air from the atmosphere and forces theair into the pressure channels by a separate air pump 92 through fiowcontrol valve 84. Either system equally insures that ammonia vapors donot escape from the developer into the atmosphere. Since the developingprocess does not require venting to the outside atmosphere, thedeveloper may be operated in a closed room.

OPERATION OF THE DEVELOPER Roll-type film having a diazo containingemulsion is transported through the developer. During the brief timethat a segment of film is within the developer it is subjected to thefollowing enumerated processes:

1. Condensation of water onto the film emulsion.

2. Diffusion of water into the emulsion to form a liquid medium for thecoupling reaction.

3. Absorption of ammonia into the water on the emulsion.

4. Diffusion of ammonia into the emulsion to neutralize the acid presentand provide an alkaline medium for reaction.

5. Coupling of the diazo salt and the coupler.

6. Removal of excess water and ammonia.

Each of these steps can be considered separately, but due to theheterogeneous nature of the chemical system, there are no doubt somepoints in the process where all of them are proceeding simultaneously indifferent parts of the film.

For example, the coupling of step 5 will occur on the surface aftercondensation of steps 1 and 3 but it can proceed deeper in the emulsiononly after steps 2 and 4. Similarly, the concentration of water andammonia deep in the emulsion may still be increasing when evaporation ofammonia and water begins from the surface. Thus, a description of theoverall process as a composite of the individual steps is complex.Nevertheless, consideration of the individual steps is useful in orderto define the several operating requirements.

When the film passes through the film seal it enters the first chamberat ambient temperature (about 25 C). The temperature of the air mixturein the chamber at this point is maintained at approximately 53 C, but

may vary between 45 C and 55 C depending on location. The dew point inthe chamber is operated between 45 and 50 C. As the comparatively coolfilm enters the chamber two processes act upon it. It is warmed byconvective transfer of heat from the surroundings, and at the same timewater condenses on the surface causing the film to be also warmed by theheat of condensation. This condensation provides the water needed forproper reaction. Thus, if the chamber temperature is too high and/or thedew point too low, the film will be warmed above the dew point before anadequate amount of water has condensed. Conversely, if the dew point istoo high and/or the chamber temperature too low, too much water willcondense and cause water spotting of the film. With the operatingtemperature of the chamber stated, an overall desired condensation ofapproximately 0.1 microns thickness will occur.

The surface coating of diazo film comprises an emulsion about 0.0003inches thick and contains the diazo salt, coupler and other stabilizingchemicals. Diffusion of water in this layer is rapid and accomplished inless than a second.

Ammonia in the vapor phase is rapidly absorbed by the water condensed onthe film until equilibrium is reached between the concentration insolution on the film and that in the vapor. For adequate development ofthe film the ammonia concentration should be sufficient to create a pHof 11 in the solution on the film. This corresponds to a minimum partialpressure of ammonia vapor in the air mixture of approximately 5 X 4atmospheres, or 500 parts per million by volume if the chamber is atatmospheric pressure. Adjustment of the ammonia level in the vapor maybe regulated by the control valve to the ammonia reservoir. A locallyhigher concentration in the ammonia tunnel will promote and acceleratethe absorption process. The proper concentration is adjusted by theammonia vapor level throughout the chamber.

The ammonia absorbed at the surface must diffuse throughout the coatingemulsion in sufficient quantity to neutralize all the acid mediumpresent in the film coating and then provide an alkaline medium of pH atleast 11. In this medium coupling of the diazo salt and coupler willoccur. I

The average film segments spend approximately three seconds transportingthrough the first chamber for the development process before loopingthrough the second chamber.

In the second chamber, the film segment is subjected to a highertemperature air mixture for approximately 2 seconds which is to removeexcess water and scavenge any remaining ammonia, and to return the filmto a dry condition on exiting the chamber. The film segment is subjectedto a final air scrubbing by the film seal before leaving the developer.

While film is threading through the developer, air is cycling aroundinside the developer in a continuous flow from chamber to chamber. Theprocess cycle for the air mixture starting at the blower is summarizedas follows:

1. Air mixture picks up water vapor to approach saturation.

2. Air mixture is heated raising its temperature farther above dewpoint.

3. Warmed air mixture passes over film prior to film egress, scavengingwater and ammonia from the film. This scavenging reduces the potentialto develop a surface haze on the film.

Air mixture passes between dam and glass, dropping temperature near orto dew point temperature.

5. Air mixture which is near or at dew point temperature comes incontact with the incoming film which is below dew point temperaturecausing moisture to condense on the film surface. Water readily absorbsammonia which causes development.

From a consideration of either the film path through the developer orthe air mixture cycle, it is clear that the thermodynamic conditionsprescribed must be maintained in the developer for proper filmdevelopment.

If for any reason the gaseous mixture temperature is not above thetemperature of the incoming film, development will not proceed properly.If the air mixture is too far above the dew point temperature too littlecondensate results. If a wide temperature differential between the filmand the air mixture exists with the air mixture close to or at the dewpoint temperature excessive condensation will cause water spotting, aphenomena which is undesirable, but does not afiect film development.

. When properly operated the developer herein disclosed is extremelyefficient from the standpoint of both developing time and materialconsumed. The improved efficiency also results in drier film leaving thechamber improving image quality because of reduced weeping or blushingof the diazo dyes.

We claim:

1. A film developer for diazo film comprising:

a. means defining a film processing zone having a film entrance and afilm exit with l. a developing area, and

2. a drying area,

. transport means for moving film through said zone from said entrancethrough said developing area hence through said drying area and thenthrough said exit,

c. air circulation means for moving air in counterflow relation to saidfilm into said drying area and hence through said developing area,

. temperature control means for heating air to maintain the air in saiddrying area hotter than the air in said developing area, and

e. supply means for supplying water and ammonia to air circulated bysaid circulating means to provide an air-water-ammonia mixture near thedew point thereof in said developing area.

2. The developer of claim 1 in which said temperature control meanscomprises means for heating air entering said drying area and means forcooling air passing from said drying area to said developing area.

3. The developer of claim 2 in which said air circulation meanscomprises a pump connected between said developing area and said dryingarea for pumping air from said developing area to said drying area.

4. The developer of claim 3 in which said pump is connected to saidsupply means for introducing water into said developer outside saidprocessing zone.

5. The apparatus of claim 4 in which said means for heating air isconnected between said pump and said drying area to heat circulating airabove its dew point after said air contacts said supply means and beforesaid air enters said drying area.

6. The developer ofclaim 4 in which said means for cooling air comprisesa wall portion of said developer and guide means for guiding circulatingair against said wall portion.

7. The developer of claim 1 in which said film exit comprises:

a. a housing having a wall with a passageway therethrough connected tosaid drying chamber,

b. a first recess in the wall of said passageway,

c. a second recess in the wall of said passageway between said firstrecess and said drying chamber,

d. ammonia absorbing means,

e. means for pumping air from said first recess, through said ammoniaabsorbing means and into said second recess.

8. A film exit for transporting diazo film from the drying chamber of adeveloping machine comprising:

a. a housing having a wall with a passageway therethrough extending outof said developer from said drying chamber,

b. a first recess in the wall of said passageway,

c. a second recess in the wall of said passageway between said firstrecess and said drying chamber,

(1. ammonia absorbing means,

e. means for pumping air from said first recess, through said ammoniaabsorbing means and into said second recess.

9. A film seal for transporting film from a processing unit comprising:

means to transport the film through the passageway without contactingthe walls of the passageway.

11. The method of developing diazo film which comprises:

a. continuously moving said film along a path in a predetermineddirection,

b. circulating air along a closed path from a first area out of the filmpath to a second area contacting the film path to a third areacontacting the film path upstream of the film path from the second areaand hence back to said first area,

0. maintaining a mixture of water and ammonia in said circulating air insaid third area adjacent to the dew point thereof,

d. heating said circulating air between said first and second areas, and

e. cooling said circulating air between said second and third areas.

12. The method of claim 11 in which said step of maintaining a mixtureof water and ammonia is performed by introducing into said closed airpath water in said first area and an i mo nia in s aid third area.

1. A film developer for diazo film comprising: a. means defining a filmprocessing zone having a film entrance and a film exit with
 1. adeveloping area, and
 2. a drying area, b. transport means for movingfilm through said zone from said entrance through said developing areahence through said drying area and then through said exit, c. aircirculation means for moving air in counterflow relation to said filminto said drying area and hence through said developing area, d.temperature control means for heating air to maintain the air in saiddrying area hotter than the air in said developing area, and e. supplymeans for supplying water and ammonia to air circulated by saidcirculating means to provide an air-water-ammonia mixture near the dewpoint thereof in said developing area.
 2. The developer of claim 1 inwhich said tempeRature control means comprises means for heating airentering said drying area and means for cooling air passing from saiddrying area to said developing area.
 3. The developer of claim 2 inwhich said air circulation means comprises a pump connected between saiddeveloping area and said drying area for pumping air from saiddeveloping area to said drying area.
 4. The developer of claim 3 inwhich said pump is connected to said supply means for introducing waterinto said developer outside said processing zone.
 5. The apparatus ofclaim 4 in which said means for heating air is connected between saidpump and said drying area to heat circulating air above its dew pointafter said air contacts said supply means and before said air enterssaid drying area.
 6. The developer of claim 4 in which said means forcooling air comprises a wall portion of said developer and guide meansfor guiding circulating air against said wall portion.
 7. The developerof claim 1 in which said film exit comprises: a. a housing having a wallwith a passageway therethrough connected to said drying chamber, b. afirst recess in the wall of said passageway, c. a second recess in thewall of said passageway between said first recess and said dryingchamber, d. ammonia absorbing means, e. means for pumping air from saidfirst recess, through said ammonia absorbing means and into said secondrecess.
 8. A film exit for transporting diazo film from the dryingchamber of a developing machine comprising: a. a housing having a wallwith a passageway therethrough extending out of said developer from saiddrying chamber, b. a first recess in the wall of said passageway, c. asecond recess in the wall of said passageway between said first recessand said drying chamber, d. ammonia absorbing means, e. means forpumping air from said first recess, through said ammonia absorbing meansand into said second recess.
 9. A film seal for transporting film from aprocessing unit comprising: a. a passageway into the processing unithaving a passageway wall b. a first recess in the wall of saidpassageway c. a second inner recess in the wall of said passageway d.air scrubbing means e. means for pumping air from said first recessthrough said air scrubbing means and into said second recess.
 10. Thefilm seal of claim 9 further comprising guide means to transport thefilm through the passageway without contacting the walls of thepassageway.
 11. The method of developing diazo film which comprises: a.continuously moving said film along a path in a predetermined direction,b. circulating air along a closed path from a first area out of the filmpath to a second area contacting the film path to a third areacontacting the film path upstream of the film path from the second areaand hence back to said first area, c. maintaining a mixture of water andammonia in said circulating air in said third area adjacent to the dewpoint thereof, d. heating said circulating air between said first andsecond areas, and e. cooling said circulating air between said secondand third areas.